Double universal joint

ABSTRACT

Double universal joint in which the conventional slidable ball and socket joint embodying the bending centre of the joint is replaced by an articulation comprising a spherical gearing. This articulation allows the bending centre to remain equally distant from each end of the joint irrespective of the bending angle, thus giving a perfect constant-velocity feature to a double Cardan joint. The articulation can be inexpensively manufactured by cold forging.

United States Patent 1 Morin July 24, 1973 DOUBLE UNIVERSAL JOINT1,665,241 4/1928 Weiss 64/21 [75] Inventor: Gerard Morin, Bondy, FranceFOREIGN PATENTS OR APPLICATIONS [73] Assignee: Societe Anonyme DBA994,934 ll/l95l France 64/21 [22] Filed: 1971 Primary Examiner-CharlesJ. Myhre [21] Appl. No.: 177,752 Assistant ExaminerRandall HealdAttorney-Ken C. Decker 30 F orergn Application Priority Data ABSTRACTSept. 11, 1970 France 7033025 Double universal oint in which theconventional slid- 52 us. Cl. 64/21 64/8 able ball and sockeljoim m yingthe bending cen- 51 1 rm. Cl. Fl6ii 3/30 i is replaced by an articulatimP 58 Field of Search 64/21 R a R a spherical gearing This articulatb"allws the bend ing centre to remain equally distant from each end of 5References Cited I the joint irrespective of the bending angle, thusgiving UNITED STATES PATENTS a perfect constant-velocity feature to adouble Cardan 3 324 683 6/1967 8 h t 64/21 joint. The articulation canbe inexpensively manufacc to er .i 2,067,286 1 1937 Pearce 64/21 turedby cold forgmg' 3,017,755 1/1962 Miller 64/21 2 Claims, 5 DrawingFigures PATENIEB JUL24 I975 SHEET 2 OF 3 DOUBLE UNIVERSAL JOINT Thisinvention relates to double universal joints and more particularlyrelates to ajoint in which the conventional ball and socket at thecentre of the joint is replaced by an improved multi-directionalarticulation.

Universal joints are well-known torque transmitting means used, forexample, in motor vehicle construction. They can tranmit the rotation ofa driving shaft to a driven shaft while allowing these shafts to bend",i.e. to move out of positional alignment. It is well known to use doubleuniversal joints which when large bending angles are to be obtained. Inconventional Cardan type joints, it is well known that a combination oftwo of these joints will correct a rotational irregularity which isparticularly pronounced when a single joint is used.

A cardan type of double joint will not, however, provide a constantvelocity transmission since the primary and secondary shafts will rotatein perfect synchronism only if both of the elementary joints forming thedouble joint have an equal bending angle, and this implies that theshafts must have an inclination such that their axes meet at a pointequally distant from each of the bending centres. The arrangementgenerally adopted for ensuring that this condition is approximatelysatisfied comprises connecting members which are disposed in alignmentwith the shafts and which are coupled to each other by a sliding balland socket joint. The latter transmits no torque and serves only as apoint of support sliding of this ball and socket joint is intended toabsorb the difference in length experienced by one of the connectingmembers when the bending angle is varied. It will be apparent that theconventional use of a sliding ball and socket joint will not give aconstant velocity transmission because it does not allow the two bendingcentres to be systematically equidistant from the point of intersectionof the shaft axes.

It is known to use sliding ball and socket joints in a similararrangement in types of double universal joint other than those whichinclude Cardan transmission couplings. When sliding ball and socketjoints are used in constant velocity double joints, the variations dueto the sliding of the ball and socket joint do not destroy the constantvelocity feature of the double joint but they do prevent the use ofcertain advantageous arrangements which would allow dimensions to bereduced.

The sliding ball and socket joint is always a relatively complexcomponent because it requires spherical machining and, in particular,the machining of a spherical recess covering a solidangle of more than180.

. The present invention provides a double universal joint wherein thesliding ball and socket joint is advantageously replaced by an improvedarticulation. The invention also covers this improved articulation.

In the double universal joint according to the invention, thearticulation which replaces a sliding ball and socket joint is formed bytwo adjacent heads, the confronting surfaces thereof respectivelycomprising at least one annular depression and at least one annularprojection which, in axial section, have the profile of gearing teeth,the projections on one of the heads being received in the depressions inthe other head and forming a spherical gearing system in which at leasttwo adjacent teeth are in contactive engagement for any bending anglewithin a given solid angle.

The resulting articulation has none of the disadvantages of a ball andsocket joint, because the two heads of this articulation roll on oneanother in every direction in the same way as two gear sectors roll onone another in a single direction, and hence with equal angles ofrotation when the vector radii are equal and the centres of rotation arefixed. In addition, the articulation is relatively inexpensive, becauseit can be made by cold forging with sufficiently narrow tolerances tomake any subsequent machining unnecessary. This articulation cantherefore be used advantageously in all types of double universaljoints.

The invention will now be described by way of example with reference tothe accompanying drawings wherein FIG. 1 shows a Cardan type doublejoint of conventional used, to define the object of the invention.

FIG. 2 is an elevation in partial section and partial broken-away form,showing a Cardan type double joint using the articulation according tothe invention.

FIG. 3 is a section of the articulation on the line 3-3 in FIG. 2.

FIGS. 4 and 5 are elevations, partially in section and partially brokenaway, of double constant velocity joints using the articulationaccording to the invention.

FIG. 1 illustrates a conventional Cardan type double joint to whichreference will be made in order to explain the object of the invention.

A double joint of this type is reversible; the components on the primaryside are similar to the components on the secondary side and have thesame references.

It will be apparent that the head T of each of the shafts A is mountedpivotally on a cross-member or spider K. The two spider members K arethemselves pivotable relatively to a cage C holding them in spacedrelationship. The joint consequently permits each of the shafts A tooscillate in two mutually perpendicular directions and it also permits arotational movement to be transmitted from one shaft to the other.

Two rods P connected to the shafts A via the shaft heads T extend withinthe cage C and in alignment with the shafts A. The free ends of the rodsP are coupled to one another by a sliding ball and socket joint R. Theball and socket joint R causes each of the shafts A to assume theinclination a or B with respect to the aligned position of these shafts.The angles a and B are equal when the centre of the ball and socketjoint R is equally distant from the centre of each of the spider membersK and, when this condition is satisfied, the rotational movement of oneshaft is transmitted integrally to the other shaft. On the other hand,when angle a is not equal to angle B, the rotational movement istransmitted with some fluctuation in rotational velocity.

The conventional Cardan type double joint shown in FIG. 1 has not aperfect constant velocity feature, because thecentre of the sliding balland socket joint R does not remain equally distant from the spidermembers K when the inclination of the shafts varies, thus causing theangles a and B to be generally unequal.

The object of the invention is to replace the sliding ball and socketjoint R by an articulation which allows the angles 0: and B to remainequal, irrespective of the inclination of the shafts.

FIG. 2 illustrates a Cardan type double joint wherein the sliding balland socket joint is replaced by an articulation according to theinvention, this articulation being generally designated by the letter S.The construction of this double joint is fundamentally the same as thatof the double joint shown in FIG. 1 and like parts are designated by thesame numeral references. FIG. 2 includes various details which will notbe described because they are well-known and do not directly relate tothe invention; for example, the bearings 2 which serve as pivots for thespider members K will not be described.

The extensions P of the shafts A are fitted into the heads T of theseshafts they extend through a central aperture in the spider members Kand then are connected to the articulation S. This articulation isenclosed in a flexible protective envelope 4 which if desired maycontain a lubricant.

Referring to FIGS. 2 and 3, the articulation S is formed fundamentallyfrom two parts 6, 8 whose cross section is circular and whose axialsection has the profile of gear teeth, one of the elements, i.e., 6having an annular projection 10 which is received in an annular groove12 in the element 8. As shown, the element 6 comprises two teeth and theelement 8 three. The profileof the gear teeth referred to may be aconventional profile of involute form. With this articulation, the shaftextensions P can bear on one another while moving angularly in everydirection and over solid angles as great as the bending angles which areobtainable with a sliding ball and socket joint.

Using the articulation S according to the invention, the Cardan typedouble joint shown in FIG. 2 is a constant velocity joint because,irrespective of the inclination of the shafts A, the contact points ofthe elements 6, 8 are situated on pitch circles s1, s2 which define thegearing. Provided that circles s1, s2 have an equal radius and theircentre coincides with the centre of the spider members K, the axes ofthe shafts A always intersect in the central plane 3-3. The point ofintersection of the axes is therefore always equidistant from thecentres of the spider members K and the two shafts are always equallyinclined.

FIG. 4 showsa modification of the invention wherein the articulation isused in a double joint formed from the constant velocity elementaryjoints of the type having two interlaced arms and four balls.

In the double joint, the arms of each head T are interlaced with twoarms carried by the cage C, and the balls 14 are interposed between thearms. The centres of the four balls belonging to each elementary joint,hence the centre of rotation of the joint, are always contained in thesame plane, irrespective of the inclination of the shafts.

The rods P are connected to an articulation S of the same type as thatdesignated by the same reference in FIG. 2. Each of the rods P is,however, articulated on a ball and socket joint 16 in which a sphericalpart is integral with the rod P, a concave part'is connected to the rodC, and a bending centre coincides with the centre of rotation of thejoint. The double joint is surrounded by a flexible protective envelope18.

In the case of the-double joint shown in FIG. 4, the advantage of thearticulation S does not lie in the fact that the shafts A retain anequal inclination, because the constant velocity feature inherent ineach elementary joint exists for the entire joint irrespective of theinclination of the shafts. The double joint simply allows larger bendingangles to be obtained.

Even so, it is advantageous to use the articulation according to theinvention because it is cheaper than the sliding ball and socket jointwhich was hitherto used instead. Both the element 6 and the element 8are readily ejected and can be made with excellent accuracy by coldforging.

FIG. 5 illustrates an alternative embodiment of the double joint formedfrom two constant velocity elementary joints of the type having twointerlaced arms and four balls.

In this variant, each of the rods P is articulated on a ball and socketjoint 20, the centre of which is located within the space defined by theplanes intersecting the four balls 14 of either elementary joint i.e.,interiorly with respect to the centre of rotation of the corre spondingelementary joint. Interiorly with respect to the centre of rotation ofeach joint, each rod P is connected to a head T by a flexible connection22 which is shown as a ball and socket joint in the drawing but whichcould as well be a resilient sleeve. As before, the rods P are connectedto an articulation S which forms a spherical gearing, and it will benoted that in this embodiment the element 6 of the articulation has justone tooth and the element 8 has two teeth.

The embodiment shown in FIG. 5 eliminates a need which in the case ofFIG. 4, demanded that the centre of the ball and socketjoints 16 shouldcoincide with the centre of rotation of each elementary joint. As aresult there are variations in the alignment between the rods P and theshafts A, but these variations are absorbed by the flexible connections22 provided between the-rods P and the heads T.

As previously described, the articulation S forms a spherical gearingsystem on which the rods P can bear under conditions such thatirrespective of the angle formed by the rods within the permitted limitsthe axes of these rods will meet a point equally distant from thecentreof rotation of the rods, said centre of rotation being embodied bythe centre of the joints 20.

I claim l. A double universal joint in which a first elementary jointand a second elementary joint each comprise an input element and anoutput element, the assembly of which allows a torque to be transmittedwhile enabling said elements to pivot independently in any directionabout a center of rotation, an element of the first elementary jointbeing connected to an element of a second elementary joint by a singlehollow member or cage, while the other element of each elementary jointis simultaneously connected to a shaft end and to a support rod, saidsupport rod extending within the space inside the said cage and beinginterconnected approximately at the center of said space by means of amultidirectional articulation, said double universal joint beingcharacterized in that the multi-directional articulation is formed bytwo adjacent heads, the confronting surfaces thereof respectivelycomprising at least one annular depression and at least one annularprojection which, in axial section, have the profile of gearing teeth,the projection on one of the heads being received in the depressions inthe other head to form a spherical gearing system in which at least twoadjacent teeth are in contactive engagement for any relative inclinationof the support rods at an angle within a given solid angle;

said first and second elementary joints being constant-velocity jointshaving two interlaced arms and four balls, and further characterized inthat each support rod is connected to one of said joint elements rigidlyand coaxially to the shaft connected to the same element, the rod beingfurther articulated on said cage by a ball and socket joint at thelocation of the center of rotation of the corresponding elementaryjoint.

2. A double universal joint in which a first elementary joint and asecond elementary joint each comprise an input element and an outputelement, the assembly of which allows a torque to be transmitted whileenabling said elements to pivot independently in any direction about acenter of rotation, an element of the first elementary joint beingconnected to an .element of a second elementary joint by a single hollowmember or cage, while the other element of each elementary joint issimultaneously connected to a shaft end and to a support rod, saidsupport rod extending within the space inside the said cage and beinginterconnected approximately at the center of said space by means of amultidirectional articulation, said double universal joint beingcharacterized in that the multi-directional articulation is formed bytwo adjacentheads, the confronting surfaces thereof respectivelycomprising at least one annular depression and at least one annularprojection which, in axial section, have the profile of gearing teeth,the projection on one of the heads being received in the depressions inthe other head to form a spherical center of rotation.

1. A double universal joint in which a first elementary joint and asecond elementary joint each comprise an input element and an outputelement, the assembly of which allows a torque to be transmitted whileenabling said elements to pivot independently in any direction about acenter of rotation, an element of the first elementary joint beingconnected to an element of a second elementary joint by a single hollowmember or cage, while the other element of each elementary joint issimultaneously connected to a shaft end and to a support rod, saidsupport rod extending within the space inside the said cage and beinginterconnected approximately at the center of said space by means of amulti-directional articulation, said double universal joint beingcharacterized in that the multi-directional articulation is formed bytwo adjacent heads, the confronting surfaces thereof respectivelycomprising at least one annular depression and at least one annularprojection which, in axial section, have the profile of gearing teeth,the projection on one of the heads being received in the depressions inthe other head to form a spherical gearing system in which at least twoadjacent teeth are in contactive engagement for any relative inclinationof the support rods at an angle within a given solid angle; said firstand second elementary joints being constant-velocity joints having twointerlaced arms and four balls, and further characterized in that eachsupport rod is connected to one of said joint elements rigidly andcoaxially to the shaft connected to the same element, the rod beingfurther articulated on said cage by a ball and socket joint at thelocation of the center of rotation of the corresponding elementaryjoint.
 2. A double universal joint in which a first elementary joint anda second elementary joint each comprise an input element and an outputelement, the assembly of which allows a torque to be transmitted whileenabling said elements to pivot independently in any direction about acenter of rotation, an element of the first elementary joint beingconnected to an element of a second elementary joint by a single hollowmember or cage, while the other element of each elementary joint issimultaneously connected to a shaft end and to a support rod, saidsupport rod extending within the space inside the said cage and beinginterconnected approximately at the center of said space by means of amultidirectional articulation, said double universal joint beingcharacterized in that the multi-directional articulation is formed bytwo adjacent heads, the confronting surfaces thereof respectivelycomprising at least one annular depression and at least one annularprojection which, in axial section, have the profile of gearing teeth,the projection on one of the heads being received in the depressions inthe other head to form a spherical gearing system in which at least twoadjacent teeth are in contactive engagement for any relative inclinationof the support rods at an angle within a given solid angle; said firstand the second elementary joints being constant-velocity joints havingtwo interlaced arms and four balls, and further characterized in thateach support rod is connected to one of said joint elements by aflexible connection and exteriorly with respect to the center ofrotation of the corresponding elementary joint, the rod also beingarticulated on said cage by a ball and socket joint inside the center ofrotation.